Process of separating substantially pure ferrous chloride from a mixture of fecl2 and cocl2



Patented May 4, 1954 PROCESS OF SEPARATING SUBSTANTIALLY PURE FERROUS CHLORIDE FROM A MIX- TUBE 0F FeClz AND CoClz Marion Ernest Graham, Parma, and Edward A. Beidler, Columbus, Qhio, assignors, by mesne assignments, to Republic Steel Corporation, Cleveland, Ohio, a corporation of New Jersey No Drawing. Application June 4, 1952, Serial No. 291,816

4 Claims.

Our present invention relates to a process or separating substantially pure ferrous chloride from a mixture of ferrous chloride and cobalt chloride, the ferrous chloride so separated to have a content of cobalt chloride not over about 0.5%. A particular embodiment ofthe invention may constitute one stepof a large overall process of treating solid mixtures of iron with cobalt and possibly other metals, which mixtures are obtained by treating ores or alloys containing these metals or some of them, and possibly other metals in the case of alloys and natural ores, and also gangue in the case of ores. In the overall process, above generally referred to, the first step of the process, which forms no necessary part of the present invention, is to chloridize the original material. This converts a substantial amount of the iron present in the original material to ferrous chloride. Some of the iron may, however, be originally present in the form of metallic iron or may be converted to metallic iron. This is particularly true in the event that the chloridizing is accompanied by a reducing action provided in any appropriate way. Cobalt, if present, will be converted at least in part, to the form of cobalt chloride, C0012, while some of this metal may be present in, or be converted to, the metallic form in the same way as the iron. Other metals may, for example, be present in the original material being treated, for example, chromium, when the material is stainless steel scrap or certain types of ores. Gangue may also be present in the event that the original material is a natural ore, this gangue being alumina, silica, possibly also magnesia or more or less complex compounds of these materials commonly found in natural ores.

The present inventionrnay be considered as being applicable following the chloridizing of the original material, whatever it may be and whatever its source may be. As such, the essential active ingredients of the material forming the input to the processof the present invention are (a) ferrous chloride (FeClz) and (b cobalt chloride (00612) in an. amount greater than about 0.5% of the B3012, which is permissible in the ferrous chloride as separated.

The general purpose of the present invention to enable the ferrous chloride to be separated from the remaining materials in a commercially to a non-volatile form, such as elemental cobalt. It is recognized that the elemental cobalt thus formed may not remain as such, but may possibly combine with the metallic iron originally present as aforesaid, to form some cobalt-iron alloy. However, the broad purpose is to retain a maximum amount of the cobalt in a non-volatile form, while separating substantially pure FeClz therefrom by vaporization.

In the prior art illustrated, for example, in the patents to Kroll Nos. 2,396,792-3-4, all issued March 19, 1946, an attempt was made to separate various metallic impurities from nickel. The disclosures of these Kroll patents are summarized in our copending application entitled, Process of Preparing Ferrous Chloride from Mixed Chlorides of Iron and Nickel, Serial Number 160,821, filed May 1950. In accordance with these Kroll patents, a transfer reaction can take place be tween iron in elemental form and nickel chloride, so as to form nickel in elemental form and forrous chloride. In one of these patents, Kroll discloses specifically that the chemical transfer reaction aforesaid is a reversible type reaction which proceeds only to some intermediate equi-' librium stage. In order to bias the equilibrium in a desired direction, Kroll resorted to the expedient of adding a substantially large excess of nickel chloride, 25% to 50%, for example.

The present application is one of a group of seven co-pending applications, all the inventions of the same inventors, four of these cases relating to nickel and reactions involving nickel and the other three relating to cobalt and reactions involving cobalt. The cases may be compared and distinguished as follows:

a. Ser. No. 160,821, filed May 8, 1950, relates to treating a starting material in the non-gaseous -(lic uid and/or solid) form and consisting essentially of NiClz and Feclz, and wherein there is more FeClz than NiClz. This starting material is treated in a reaction or sublimation zone, in the presence of a certain amount of metallic iron, to produce a final product which is vaporized FeClz, removed from the sublimation zone as such, leaving only metallic iron and metallic nickel in the sublimation zone.

1). Ser. No. 210,433, filed February 10, 1951, relates to treating a starting material, essentially the same as Ser. No. 160,821, except that in this instance the starting material is introduced into the reaction zone in a solely gaseous state. The reaction and the final products are substantially the same as in Ser. No. 160,821.

0. Ser. No. 160,822, filed May 8, 1950, relates to the preventing or minimizing of a possible back reaction. The starting material consists essentially of ferrous chloride and metallic nickel. It is desired to separate these materials without permitting, or at least minimizinga possible back reaction therebetween which would produce nickel chloride and metallic iron. To do this, the starting material is introduced into a reaction or sublimation zone in which metallic iron is present. The starting material as introduced into this zone is in a non-gaseous state. The final products are substantially pure ferrous chloride vapor, which is removed from thezone-as .such, and metallic nickel and metallic'iron' which remain in the zone.

at. Ser. No. 294,058, filed June 17,1952, discloses a process for treating a starting material substantially the same as in Ser. No. 160,821. This case has been amended so as to preclude the claims reading upon separation of the products of the reaction by vaporization as inSer. No. 160,821; but in this case the separation following the reaction is effected by withdrawing the metallic nickel produced (by-a reaction the same asin Ser. No. 160,821.) by withdrawing massivepieces of iron, to which the deposited nickel'adheres physically, from the fused bath of the starting materials. Neither the ferrous chloride nor any nickel chloride present is intentionally volatilized. This application is junior "to application Ser. No. 160,821, so that the only subject matter claimable therein is subject matter which cannot be supported by the disclosure of Ser. No. 160,821; all the common subject matter being claimed in Ser. No. 160,821.

e. Ser. No. 291,816, filed June 4, 1952 (the present application) is the first of the three cobalt applications and is the cobalt counterpart'of the nickel case, Ser. No. 160,821, distinguishing therefromby being directed to cobalt andits chloride, rather than nickel and its respectivechloride. This case is further distinguished in the degree of purity of the sublimate.

1. Ser. No. 320,835, filed November 15, 1952, is the cobalt counterpart of nickel case, Ser. No. 210,433. It distinguishes from cobalt caseSer; No. 291,816 in the same way discussed above as to the respectively corresponding nickel cases, while distinguishing from its corresponding nickel case,

Ser. No. 210,4:33, by the differences betweencobaltand nickel.

q. Ser. No. 321,514, filed November 19, 1952, is the cobalt case corresponding to the nickel case Ser. No. 169,822; It distinguishes from the other cobalt-cases as discussed above inrespect'to-the respectively corresponding nickel cases, while distinguishing from its nickel counterpart, Ser. No. 160,822, by the (inferences between nickel and cobalt.

In accordance with the present invention, "the separation to be carried out, in'accordance'with the present process, is between ferrous chloride and cobalt chloride, rather than between ferrous chloride and nickel chloride as disclosed in the Kroll'patents aforesaid and in our copending application aforesaid. Although the chemical behavior of the chlorides of nickel and cobalt "are somewhat similar, as is to be expected from their relative positions in the periodic tableof elements, there are certain differences in their chemical behavior which make the particular processes disclosed in the Kroil patents aforesaid, or in our above-identified copending application, inapplicable to the separation of subtantially pure ferrous chloride from cobalt chloride.

The basic material to be worked upon, in accordance with the present process, is contemplated to contain relatively larger percentages of iron in the form of ferrous chloride, as compared with the amount'of cobalt chloride present. Such material is to be contrasted with the type of material to be treated, in accordance with the Kroll patents which are apparently adapted only for treatm'entof materials containing a substantially large excess of nickel chloride, as pointed out above. For example, in one ore which has been treated in accordance with the present process, there is containedlabout 40 times as much iron as cobalt.v This difference in raw material, however; is'not presently relied upon as a basic distinction from=the prior art, but is mentioned as illustrating a difference in the type of material. which the present invention is adapted to treat, as compared with the material contemplated for use in the closest known prior art.

Inv accordance with our copending'application hereinbefore referred to, there was contemplated a substantially complete separation'between ferrousr chloride and nickel chloride, so as to form therefrom ferroustchloride by thechemicaltransfer reaction represented byv the equation:

Preferably, in that application, there was initially present a reasonable excess of elemental iron over the equivalent or stoichiometric proportions required. While the process of the present invention also utilizes a chemical transfer reaction represented by a similar equation, namely:

(2) Fe+CoCl2=FeClz+Co it hasbeenifoundthat in order to cause the last named reaction to carry through to a substantialdegree of'completion, i. e., to convert a maximumamount ofmthe cobaltr'chloride present to some non-volatileform of=coba1t; such as metallic cobalt and to produce substantially pure FeClz, at least about three times as much metallic iron must be present :as would be theoretically necessary' to react with all of the chlorine initially present in the form of cobalt chloride/in accordance with the chemical equation set forth above. In other words; there is. required an amount of iron at least'about three times the stoichiometric equivalent of the chlorine introduced into the 'processin the form 'Of'COClz in accordance with Equation 2 above. While the transfer reaction (2) isbasically similar to that whichwas contemplated in accordance with the Kroil patentsth'eretofore mentioned, in the present case the reactionis caused to carry through to a maximum and commercially practicable extent irrespective of ithereveisible character of the'rea'ction' and some intennediate end point, by separating the ferrous chloride from the process substantially as it is formed. Specifically, the present invention contemplates the distillation separation Of substantially pure ferrous chloride as a product, including both the ferrous chloride which is initially-present in'the material supplied to the process and that which is formed by the chemical transfer reaction aforesaid. For this purpose, the temperature will be adjusted to a point such'that the ferrous chloride present will havean appreciable vapor pressure and, if necessary, a sweep gas will be used to convey the ferrous chloride vapor away from the remaining unvolatilized materials.

Considering now the details of the present process, the sources of-the materials going into the process are wholly immaterial. Any preliminary steps effected on such raw materials form no part of the present invention. The material entering the process in all instances con-- tains ferrous chloride, FeClz, and further contains cobalt chloride, CC12, the latter being present in an amount of substantially over 0.5% based upon the ferrous chloride present. This starting material may or may not contain one or both of the metals, iron and cobalt, in elemental form. It may also contain more or less, or even none, of other metallic oxides or chlorides, or some inert earthy materials as are generally classed as gangue in the metallurgical field.

It has been found that the requirements of an excess of metallic iron are generally greater in the present process as compared with the process of our copending application, Serial Number 160,821 aforesaid, relating to treatment of mixtures of FeClz and NiClz. Thus, where it is desired effectively to separate cobalt chloride from ferrous chloride, in accordance with the present invention, by utilizing the exchange reaction represented by the Equation 2 above, it has been found that at least about three times the weight of metallic iron must be present as would be theoretically (stoichiometrically) sufficient to react with all of the chlorine initially present in the form of cobalt chloride. As will be more particularly pointed out in subsequent examples, the amount of cobalt chloride con verted to non-volatile cobalt and the consequent purity of the ferrous chloride distilled from the mixture in accordance with the equation set forth above, is dependent to a substantial degree on the amount of excess metallic iron present; and in order to obtain what is considered a commercially practicable separation between the two chlorides which, for the purpose of the present invention, means providing a ferrous chloride sublimate containing not over about 0.5% COClz, the amount of metallic iron in the reaction mixture must be at least about three times the chemical (stoichiometric) equivalent of the cobait chloride initially present, in accordance with the Equation 2 set forth above. It has also been found and will be particularly pointed out in the subsequent examples, that the presence of metallic iron in amounts greater than about three times the chemical or stoichiometric equivalent of the cobact chloride initially present does not appreciably enhance the eifectiveness of the separation, in that it does not substantially reduce the cobalt chloride content of the FeClz sublimate. anomalous behavior on the part of cobalt chloride or for its unexpected difference from nickel chloride is presently known. to applicants.

In some starting mixtures of materials which may be sup-plied to this process, there may be an adequate amount of metallic iron present to comply with the requirements of the process, as hereinabove set forth. In such an event, it will be unnecessary to add metallic iron. In other materials supplied to the process, it will be practically necessary to add some iron. In such an event only, an addition of iron is an essential step of the present process. The term providing metallic iron or equivalent language as used in the appended claims, includes either a starting material which has an adequate amount of metailic iron present initially, or a starting material which did not initially contain sufficient or any metallic iron, but to which metallic iron has been added.

No theoretical reason for this apparently The present process is effected primarily as a single step, during which the material is maintained at a desired temperature or within a selected desired temperature range. In the event that the material comes from a prior process, at the termination of which it is already heated, it may be suil'lcient to maintain it at the temperature which it has on entering the present process. However, in the usual case, it will be necessary to heat the material. The temperature range in the present case is that in which the vapor pressure of ferrous chloride is sufliciently great, so that it may volatilize at a desired rate. As will be understood, the vapor pressure of ferrous chloride increases progressively with increasing temperature. Thus, there is no definite or critical low limit of temperature for the present process. In some instances, it may be desired to operate at a temperature even less than the melting point 6.1 ferrous chloride. However, for practical purposes, the results obtained at temperatures lower than about 700 C. are so small from the point of view of the rate of sublimation or distillation of FeCls that this temperature may be considered the low limit for the process for the purposes of this invention. Below about this temperature, the vapor pressure of ferrous chloride is so low that the rate of volatilization thereof is below an economically practical value. At the same time, the actual temperature to be chosen above the predetermined low limit will depend primarily upon economics and upon factors other than temperature itself.

The high temperature limit is believed to be about that of the boiling point of ferrous chloride which, at atmospheric pressure, is about 1025 C. In View of the fact that the volatilization of ferrous chloride is an endothermic process, the temperature of the solid (and/or liquid) mass cannot exceed this boiling point as long as any substantial amount of ferrous chloride remains nonvolatilized. The vaporization of ferrous chloride, which absorbs heat, will keep the temperature from exceeding about this boilin point, as long as there is any ferrous chloride present in either solid or liquid form. The high temperature limit, therefore, is selected as about the boiling point of ferrous chloride at the pressure present. It will be understood, however, that in some installations it may be possible to maintain the materials under super-atmospheric pressure, in which event a somewhat higher absolute temperature limit would be permissible for use, in that the boiling point temperature of ferrous chloride is a function of pressure.

It may be desired, and is to be included in the purview of the present invention, that the process be carried on at temperatures lower than the actual melting'point temperatures of the iron and cobalt chlorides present. In general, it may be said that while the temperature is not particularly critical, the rate of removal of ferrous chloride from the material is, of course, a function of temperature, so that the process is completely operative throughout a large temperature range as stated, the rate dizlering for different temperatures. A temperature and a time period for the process are, therefore, joint functions each of the other; and both, of the amount of ferrous chloride present initially, plus the amount of ferrous chloride which is formed in accordance with the process.

In the event that the temperature of the reaction, as'aforesaid, is to be maintained substantially at the boiling point of'ferrous chloride, then this material would havea suflicient vapor pressure so. thatit would pass from the solid material without assistance and .per se flow out of the system to a point to which'it is desired to pass the ferrous chloride vapor. If, on the other hand, some lower temperature is employed, which is within the scope of the'present invention as aforesaid, then some sweep gas should be used in order that the ferrous chloride vapor be separated from the unvolatilized material remaining and be passed to a desired point. It is usually contemplated, in accordance with the present invention, that any'sweep gas employed will be essentially neutralor inert in character, in respect to the various materials which are or may be present, such, for example, as nitrogen. Some other gas or gases may be useful alone or in combination where the effect of the gas present is not sufiicient to change the reaction taking place in an undesired manner.

In the normal operation, in accordance with the present process, ferrous chloride vapor will be conveyed out of the apparatus in which the reaction proper is carried T011, hereincalled a reaction Zone, and to some other apparatus. It is contemplated that the present process may be carried on, either as an intermittent 0r batch process on the one hand, or as a continuous. or semi-continuous process on the other, and in any desired type of apparatus which will be appropriate. The present invention is not restricted to any one type of-apparatus; but many will suggest themselves to those skilled in the art from the present description of'the process itself.

It is contemplated that under. certain circum stances, ferrous chloride vapor of the purity obtained by the present invention (not over about 0.5% CoCla) may be desired for use in certain subsequent processes as such. vapor may be passed directly to such further process.

On the other hand, it may be desired to condense this vapor to a liquid and/or solid condition. If so, such condensation may be carried on in any appropriate condensing apparatus, from which the heat of vaporization may be recovered by any suitable heat-recovering system, if desired. The subsequent use of the'ferrous chloride vapor produced by the present process forms no necessary part of the present invention and hence will not be further described herein.

The materials remaining at the termination of the operation of the separation of the ferrous chloride therefrom, in accordance with the present invention, may be further processed forthe recovery of one or more of the valuable ingredients thereof. For example, cobalt may be recovered from this material by any suitable process, for example, by mechanical or magnetic separation or by some chemical treatment involving one or more steps, all of which, per se, form no part of the present invention. Such process for the recovery of metal values may include any of those well known in the art and will not be further discussed herein.

The process of the'present invention is further illustrated by the following examples:

EXAMPLE I Theprocess was operated using a mixtureof 92.6% FeClz, 2.87% CoClz and 5.12% metallic iron, all by weight, at a temperature of about 700 C. for about 3 hours. The sublimate .obtained by this treatment amounted to only about If so, then this 8 16.1% of the total weight or the charge, indicating that a temperature of about 700 C. is about the minimum temperature at which FeClz has suflicient vapor pressure to permit its vaporization at a reasonable rate.

EXAIVIPLE II This example illustrates the necessity for providing some metallic iron in the mixture of FeClz-CoClz inorder to obtain a sublimate substantially free from CoClz in accordance with the present invention. A mixture of FeCl: and C0012, containing about 97.5% FeClz and 2.5% C0012, by weight, and substantially free of metallic iron, was heated in a stream of nitrogen for about one hour at 1000 C. In this time substantially all of the Feclz present had been sublimed. The sublimate was found to contain 1.65% by weight C0012 with the balance FeClz. Since this test was carried out in the absence of metallic iron, it served as an experimental confirmation of data previously available, that the vapor pressures of FeClz and C0C12 are so close together that they can not be effectively separated by simple fractional sublimation methods, since the sublimate obtained was almost as rich in 00012 as was the original starting material.

EXAMPLE III In order to illustrate the relation between the purity of the FeClz in the sublimate obtained (as measured by its COClz content) and the quantity of metallic iron added to the starting material, reference is made to Table 1 below. The data in this table is based on tests carried out at 1000 C. using FeCh-CoClz mixtures containing these compounds in the ratio of 40 parts by weight of Feclz to one part by weight of C0012. The term stoichiometric quantity as used in the heading of the table, refers to the amount of metallic iron that would theoretically be sufiicient to react with all the COClz initially present in the mixture to form FeClz and metallic cobalt.

Table 1 Ratio of Amount of Metallic Iron present to stoichiomcttic quantity From the above data, it Will be apparent that the C0C12 content of the sublimate decreases sharply as the-excess of metallic iron increases. It will further be seenthat this'decrease becomes less pronounced with additions of iron in excess of about three times the stoichiometric quantity. For this reason, and because a sublimate containing less than one-half of one percent of C0C12 as an impurity may be considered as substantially pure FeClz, it is believed that an amount of iron equivalent to about three times the theoretical quantity necessary to react with all the C0C12 in the starting material, is about the minimum amount necessary to obtain a substantially pure FeClz sublimate. The above data also illustrates that the presence of metallic iron in excess of about three times the stoichiometric equivalent of the CoCl-z present is somewhat beneficial to the desired reaction, so that there appears to be no absolute upper limit on the amount of metallic iron which may be present. Amounts of iron greater than about three times the stoichiometric quantity may be employed in cases where F8012 sublimates of extremely high purity are desired.

EXAMPLE IV This example illustrates the process applied to a starting material, which is relatively rich in C0012, as compared to the mixtures referred to above in Example III. As demonstrated by this example, practically the same results may be obtained irrespective of the ratio of FeClz to 00012 in the original starting material.

A mixture containing equal weights of FeClz and 00012 was heated to 1000 0. with an amount of metallic iron present equivalent to five times that theoretically necessary to react with all the 00012 present. When this material was completely sublimed, it was found that the sublimate contained only 0.27% 00012 by weight. By comparing this figure with the equivalent figure (0.22%) in Example III (Table 1), it will be seen that the ratio or FeClz to 00012 in the starting material is not critical insofar as the practice of the present invention is concerned.

This conclusion is further confirmed by the fact that when a similar test was performed using as a starting material a mixture containing equal weights of FeClz and 00012, to which an amount of metallic iron ten times the stoi-chiometrio quantity was added, a sublimate containing only 0.09% of 00012 was obtained. The purity of this sublimate was thus about the same (within experimental error) as the purity of the sublimate obtained by heating a mixture much leaner in 00012 with an equivalent amount of metallic iron, as set forth in the bottom line of Table 1 in Example 111 above.

While we have described our process in general and have set forth in some detail the chemical and physical requirements thereof, it is recognized that the process may be practiced by the substitution of such equivalents as will suggest themselves to those skilled in the art from the foregoing disclosure. We do not wish to be limited, therefore, except by the scope of the appended claims, which are to be construed validly as broadly as the state of the prior art permits.

10 What is claimed is: l. The process of separating ferrous chloride having not over about 0.5% 00012 contained therein from a starting material containing both maintaining the materials including said metal- Eic iron in said reaction zone within the temperature range of about 768 C. to about the boiling point of FeClz at the pressure existing in said zone and for a time and under conditions sufiicient in conjunction with the vapor pressure of FeClz to vaporize the FeClz present in said starting material and the FeClz which is formed by a reaction between the metallic iron present in said zone and 00012 introduced into said zone in said starting material, and removing FeClz vapor having not over about 0.5% 00012 contained therein from said reaction zone.

2. The process according to claim 1, wherein the temperature at which said material is maintained is about the boiling point temperature of ferrous chloride at the pressure to which said material is exposed.

3. The process according to claim 1, comprising the additional step of assing over said material a sweep gas, which is inert in respect to all materials present, so as to assist in the removal from said material of the vapor or Fe0lz.

4. The process according to claim 1, wherein the temperature at which said material is maintained is about 1025 0., while maintaining said material at about atmospheric pressure.

References Cited in the file of this patent UNITED STATES PATENTS Number 

1. THE PROCESS OF SEPARATING FERROUS CHLORIDE HAVING NOT OVER ABOUT 0.5% COCL2 CONTAINED THEREIN FROM A STARTING MATERIAL CONTAINING BOTH FECL2 AND AN AMOUNT OF COCL2 SUBSTANTIALLY GREATER THAN 0.5% OF THE FECL2 PRESENT, AND IN WHICH THERE IS A GREATER AMOUNT OF FECL2 THAN COCL2, WHICH COMPRISES THE STEPS OF INTRODUCING SAID MATERIAL INTO A REACTION ZONE IN A NONGASEOUS STATE, PROVIDING IN SAID REACTION ZONE AN AMOUNT OF METALLIC IRON WHICH IS AT LEAST THREE TIMES THAT AMOUNT STOICHIOMETRICALLY EQUIVALENT TO ALL THE CHLORINE INITIALLY PRESENT IN SAID MATERIAL INTRODUCED INTO SAID ZONE IN THE FORM OF COCL2 IN ACCORDANCE WITH THE EQUATION 